The proposed program will encompass two main areas of investigation: 1. The structure of the various classes and subclasses of human immunoglobulins and their variants in an effort to relate this to their specific functional properties, their evolutionary origin and their genetic control. 2. Chemical and immunologic characterization of the two types of amyloid, their biosynthesis and mechanisms for their deposition and formation. BIBLIOGRAPHIC REFERENCES: Michaelsen, T.E., Frangione, B. and Franklin, E.C.: The amino acid sequence of a human immunoglobulin G3m(g) pFc' fragment. J. Immunol., in press, 1977. Michaelsen, T., Frangione, B. and Franklin, E.C.: Primary structure of the "Hinge" region of human IgG3. Probable quadruplication of a 15-amino acid residue basic unit. J. Biol. Chem. 252:883-889, 1977.